1. Field of the Invention
The present invention relates to footwear and more particularly to a new and improved shock absorbing sole construction which is particularly useful for athletic shoes and the like.
2. Description of Prior Art
The modern athletic shoe is a highly refined combination of many elements which have specific functions, all of which must work together for the support and protection of the foot during an athletic event. The shoe is divided into two general parts, an upper and a sole. The upper is designed to snuggly and comfortably enclose the foot. Typically, it will have several layers including a weather-and-wear resistant outer layer of leather or synthetic material such as nylon, and soft padded inner liner for foot comfort. Current uppers typically have an intermediate layer of a synthetic foam material. The three layers of the upper may be fastened together by stitching, gluing or a combination of these. In areas of maximum wear or stress, reinforcements of leather and/or plastic are attached to the upper.
The other major portion of the athletic shoe is the sole. Designed to withstand many miles of running, it must have an extremely durable bottom surface to contact the ground. However, since such contact may be made with considerable force, protection of the foot demands that the sole also perform a shock absorbing function. This shock absorbing function has been typically performed by a resilient, energy-absorbing material, which is located as a midsole between the durable lower surface material, i.e., the outer sole and the upper. This is particularly true for training or jogging shoes designed to be used over long distances and over a long period of time.
Foot comfort for the athlete and for those who jog or walk briskly for general exercise has been the target of many and varied proposals for shoe construction. And the broad concept of using a pneumatic cushion as part of the heel and/or sole construction has been known for the better part of a century, illustratively through King U.S. Pat. Nos. 541,814 of 1895 and Maddocks 1,011,460 of 1911. In more recent years, efforts have been directed to providing substantially uniformly absorbent action along the full length of the foot, either by employing specially fabricated pneumatic sheet material (as in Sindler U.S. Pat. 2,100,492), or by incorporating a full-length inflatable bladder in the sole (as in Reed U.S. Pat. Nos. 2,677,904 and in Cortina 2,863,230), or by providing an outsole with a substantially uniform distribution of air-filled cavities over the full area of the sole (as in Gardner U.S. Pat. Nos. 4,012,855, Petrosky 4,129,951, Khalsa, et al. 4,133,118, Moss 4,170,078, and Doak 4,397,104), or by providing a tread characterized by a distributed plurality of resilient "posts" served by interconnecting channels and a common source of pneumatic pressure (as in Muller U.S. Pat. No. 4,319,412).
Other examples of the state of the art employing various pneumatic supports can be seen in the following U.S. Pat. Nos.:
______________________________________ 4,610,099 4,271,606 4,462,171 4,219,945 4,297,797 4,183,156 ______________________________________
While the foregoing prior art patents provide improvement in the areas intended, there still exists a great need to provide an improved pneumatic shock absorbing sole construction offering maximum resistance to deformation while providing high flexibility.
Accordingly, a principal desirable object of the present invention is to provide an improved construction for pneumatic or fluid filled soles having improved shock absorbing action.
Another desirable object of the present invention is to provide a fluid-filled sole which provides varying degrees of shock absorption or cushioning as needed in various parts of the sole.
Another desirable object of the present invention is to provide an improved pneumatic sole construction having improved shock absorbing resilience to the high impact forces encountered by an active person when walking, running or jumping.
Another desirable object of the present invention is to provide an improved pneumatic or fluid-filled sole construction which minimizes fluid loss.
A still further desirable object of the present invention is to provide an improved pneumatic sole of the above desirable objects which provides a relatively simple structure, lending itself to inexpensive mass-production.